*: cleanup lint tools

[rleungx]

What problem does this PR solve?

Just clean up lint tools.

What is changed and how it works?

This PR enables golangci-lint default tools except errcheck.

Check List

Tests

• Unit test

[codecov-io]

Codecov Report

Merging #1956 into master will increase coverage by 0.2%.
The diff coverage is 81.81%.

@@            Coverage Diff            @@
##           master    #1956     +/-   ##
=========================================
+ Coverage   77.86%   78.06%   +0.2%     
=========================================
  Files         170      170             
  Lines       16879    16874      -5     
=========================================
+ Hits        13142    13172     +30     
+ Misses       2714     2687     -27     
+ Partials     1023     1015      -8

Impacted Files	Coverage Δ
server/schedulers/scatter_range.go	81.29% <ø> (ø)	⬆️
pkg/btree/btree.go	87.65% <ø> (+1.5%)	⬆️
server/testutil.go	88% <0%> (-3.67%)	⬇️
pkg/mock/mockhbstream/mockhbstream.go	86.11% <100%> (-0.38%)	⬇️
tools/pd-analysis/analysis/parse_log.go	37.03% <100%> (ø)	⬆️
server/schedulers/utils.go	87.8% <100%> (ø)	⬆️
server/core/region.go	90.18% <100%> (+0.37%)	⬆️
server/schedulers/hot_region.go	88.74% <100%> (ø)	⬆️
server/schedule/scheduler.go	69.76% <100%> (ø)	⬆️
server/kv/etcd_kv.go	75.32% <0%> (-6.5%)	⬇️
... and 12 more

---

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[sre-bot]

/run-all-tests

[rleungx]

Once #1919 is fixed. We can enable errcheck